It is often necessary to know the speed of a wheel of a vehicle, e.g., an automobile or a motorcycle. For example, anti-lock braking systems need to know when a wheel is “locking up” in order to release a brake and prevent the wheel from skidding. In addition, the speed of a wheel is often used to determine the speed of a vehicle and provide an indication of the speed to an operator.
Past systems for determining wheel speed have used mechanical couplings (e.g., speedometer cables) or sensors. Typical systems employing sensors have used a magnetic ring frictionally coupled to the wheel, along with a Hall sensor to detect the magnetic field from the ring and determine the speed of the wheel. These sensor-based systems have various drawbacks including bulky size and difficulty in mounting in order to achieve the correct frictional coupling and to correctly position the sensor in the magnetic field.